The present invention relates to compositions and methods for inhibiting the release and/or biological activity of migration inhibitory factor (MIF). In particular, the invention relates to the uses of such compositions and methods for the treatment of various conditions involving cytokine-mediated toxicity, which include, but are not limited to shock, inflammation, graft versus host disease, and/or autoimmune diseases.
Septic shock is a multifaceted pathological condition characterized most prominently by deleterious hemodynamic changes and coagulopathy leading to multiple organ failure and often to death. The altered physiological mechanisms underlying the septic shock syndrome, and the cellular means by which these changes are induced and controlled, are not yet known in precise detail. In broad outline, however, a consensus view of events culminating in septic shock has emerged over the last several years. In particular, it is now generally accepted that septic shock reflects the individual, combined and concerted effects of a large number of endogenous, host-derived mediator molecules. These mediators are produced in response to initiating stimuli that indicate the host has been invaded, and the class of peptide mediators that were generally first recognized as white blood cell products have come to be known as cytokines. As mediators of toxic effects and pathological alterations in host homeostasis, these endogenous factors represent potentially attractive therapeutic targets, and septic shock remains a potentially lethal cytokine-mediated clinical complication against which there is no generally effective therapeutic approach.
Although traditionally termed xe2x80x9csepticxe2x80x9d shock, infection by a variety of microorganisms including not only bacteria but also viruses, fungi, and parasites can induce septic shock. In fact, the shock syndrome is more properly associated with the host""s response to invasion rather than just infection, as cancer and trauma, for instance, can also serve as initiators. In the case of infection by gram-negative bacteria, one of the best studied examples, it is believed that the appearance of bacterial endotoxins such as lipopolysaccharide (LPS) in the host bloodstream leads to the endogenous production of a variety of host factors that directly and indirectly mediate the toxicity of LPS, which itself is relatively innocuous for most cells. These host-derived mediators include many now well-recognized inflammatory cytokines and classical endocrine hormones in addition to a number of other endogenous factors such as leukotrienes and platelet activating factor. It is generally acknowledged, however, that the full cast of participants and each of their interrelated roles in the host response remains incompletely appreciated.
In general, those mediators that appear earlier in an invaded host are thought to trigger the release of later appearing factors. Also, many endogenous mediators not only exert direct effector functions at their target tissues, but also prime local and remote tissues for subsequent responses to other mediators. This interacting network of host factors has been termed the xe2x80x9ccytokine cascade.xe2x80x9d This term is meant to indicate the rapid extension and amplification of the host response in such a way that only one or a few initiating stimuli trigger the eventual release and participation of scores of host mediators. Although a number of features of the host response are thought to assist in fighting off invasion, an overly robust or poorly modulated endogenous response can rapidly accelerate to rapidly produce such profound alterations in host homeostasis at the cellular, tissue, and systemic levels that death may ensue within hours.
Among the interacting factors that together comprise the cytokine cascade, the cytokine known as tumor necrosis factor-alpha (TNFxcex1) is the most important identified to date. TNFxcex1 is the first cytokine to appear in the circulation after LPS challenge. The hemodynamic and metabolic alterations that result from the experimental administration of TNFxcex1 closely resemble those that have been observed in endotoxemia and septic shock. In animal models, TNFxcex1 is the only host factor which itself can initiate a lethal syndrome that mimics septic shock in detail. In this respect, TNFxcex1 can be considered a sufficient mediator of septic shock. Functionally neutralizing TNFxcex1 antagonists such as anti-TNFxcex1 antibodies are protective in otherwise lethal bacterial infections, and in this respect TNFxcex1 can be considered a necessary mediator of septic shock.
Other cytokines participate in the host response to LPS but appear later in the circulation. However, no other cytokine has been shown to be both necessary and sufficient to mediate septic shock. For example, certain interleukins (IL-1, IL-6 and IL-8) which appear in serum more than 2 hours after LPS challenge, and interferon xcex3 (IFN-xcex3) which appears after 6 hours, are thought to play a significant role in septic shock, and can be shown to contribute to lethality in certain disease models or under experimental conditions of endotoxemia. Antagonism of the effects of specific interleukins and interferons has been shown to confer a significant protective effect under certain conditions. Nevertheless, none of these other factors can itself induce a full-blown septic shock-like effect in otherwise healthy individuals, and none of these other cytokines appears to play as central and critical role in septic shock as TNFxcex1.
In view of the foregoing, TNFxcex1 stands as an ideal target for the treatment of septic shock. Unfortunately, temporal characteristics of the endogenous TNFxcex1 response suggest a significant practical limitation for this potential therapy. TNFxcex1, one of the earliest elicited mediators to appear in acute disease, rapidly peaks after bolus endotoxin challenge (30-90 minutes), and diminishes just as promptly. It is presumed that most of the damaging effects of TNFxcex1 in septic shock are completed during this early period, hence TNFxcex1 antagonists such as anti-TNFxcex1 antibodies would ideally be present at this time. Since this therapeutic window is apparently so short and occurs so early, the timely delivery of anti-TNFxcex1 based therapeutics may be very difficult to achieve clinically.
Therefore, in order utilize cytokines as targets for the treatment of septic shock and other cytokine-mediated toxic reactions, there exists a desperate need to discover additional targets that are both necessary components of the cytokine cascade and occur at a time during the endogenous response that is accessible for therapeutic antagonism in the course of clinical treatment.
Recent studies suggest that the pituitary gland may produce factors that inhibit endotoxin-induced TNFxcex1 and IL-1 production, and thus may serve as a source for potentially protective factors that may be used to treat shock and/or other inflammatory responses. (Suzuki et al., 1986, Am. J. Physiol. 250: E470-E474; Sternberg et al., 1989, Proc. Natl. Acad. Sci. USA 86: 2374-2378; Zuckerman et al., 1989, Eur. J. Immunol. 19: 301-305; Edwards III et al., 1991a, Endocrinol. 128: 989-996; Edwards III et al., 1991b, Proc. Natl. Acad. Sci. USA 88: 2274-2277, Silverstein et al., 1991, J. Exp. Med. 173:357-365). In these studies, hypophysectomized mice (i.e., animals that have had their pituitary glands surgically removed) exhibited a marked increased sensitivity to LPS injection relative to sham-operated control mice. In fact, the LPS LD100 for control mice was approximately 1-2 logs higher than that determined for the hypophysectomized mice, suggesting that the pituitary gland produces one or more factors that may act to increase the host animal""s ability to resist endotoxin challenge. Some of these studies implicate the involvement of ACTH and adrenocorticosteroids (e.g., Edwards III et al., 1991a and 1991b, supra); however, other data suggest the existence of other protective factors derived from the pituitary.
Very recently, murine macrophage migration inhibitory factor (MIF) was identified as an LPS-induced pituitary protein (Bernhagen et al., 1993, J. Cell. Biochem. Supplement 17B, Abstract E306). While it may be hypothesized that MIF is one of such protective factors capable of counteracting the adverse effects of cytokines in endotoxaemias, its role in septic shock had not been investigated prior to the present invention.
Although MIF was first described over 25 years ago as a T cell product that inhibits the random migration of guinea pig macrophages (Bloom and Bennett, 1966, Science 158: 80-82; David, 1966, Proc. Natl. Acad. Sci. USA 65: 72-77), the precise role of MIF in either local or systemic inflammatory responses has remained largely undefined. MIF has been reported to be associated with delayed-type hypersensitivity reactions (Bloom and Bennett, 1966, supra; David, 1966, supra), to be produced by lectin-activated T-cells (Weiser et al., 1981, J. Immunol. 126: 1958-1962), and to enhance macrophage adherence, phagocytosis and tumoricidal activity (Nathan et al., 1973, J. Exp. Med. 137: 275-288; Nathan et al., 1971, J. Exp. Med. 133: 1356-1376; Churchill et al., 1975, J. Immunol. 115: 781-785). Unfortunately, many of these studies used mixed culture supernatants that were shown later to contain other cytokines such as IFN-xcex3 and IL-4 that also have migration inhibitory activity (McInnes and Rennick, 1988, J. Exp. Med. 167: 598-611; Thurman et al., 1985, J. Immunol. 134: 305-309).
Recombinant human MIF was originally cloned from human T cells (Weiser et al., 1989, Proc. Natl. Acad. Sci. USA 86: 7522-7526), and has been shown to activate blood-derived macrophages to kill intracellular parasites and tumor cells in vitro, to stimulate IL-1xcex2 and TNFxcex1 expression, and to induce nitric oxide synthesis (Weiser et al., 1991, J. Immunol. 147: 2006-2011; Pozzi et al., 1992, Cellular Immunol. 145: 372-379; Weiser et al., 1992, Proc. Natl. Acad. Sci. USA 89:8049-8052; Cunha et al., 1993, J. Immunol. 150:1908-1912). Until very recently, however, the lack of a reliable source of purified MIF has continued to hamper investigation of the precise biological profile of this molecule.
The present invention relates to compositions and methods which inhibit the release and/or biological activity of migration inhibitory factor (MIF). The invention further relates to the uses of such compositions and methods for the treatment of conditions involving cytokine-mediated toxicity, which include, but are not limited to shock, inflammation, graft versus host disease, and/or autoimmune diseases.
The inhibition of MIF activity in accordance with the invention may be accomplished in a number of ways which include, but are not limited to, the use of MIF binding partners, i.e., factors that bind to MIF and neutralize its biological activity, such as neutralizing anti-MIF antibodies, soluble MIF receptors, MIF receptor fragments, and MIF receptor analogs; the use of MIF-receptor antagonists, such as anti-MIF-receptor antibodies, inactive MIF analogs that bind but do not activate the MIF-receptor, small molecules that inhibit MIF release, or alter the normal configuration of MIF, or inhibit productive MIF/MIF-receptor binding; or the use of nucleotide sequences derived from MIF gene and/or MIF receptor gene, including coding, non-coding, and/or regulatory sequences to prevent or reduce MIF expression by, for example, antisense, ribozyme, and/or triple helix approaches. Any of the foregoing methods may be utilized individually or in combination to inhibit MIF release and/or activity in the treatment of the relevant conditions. Further, such treatment(s) may be combined with other therapies that (a) inhibit or antagonize initiators of cytokine-mediated toxicity (e.g. anti-LPS antibody); (b) inhibit or antagonize toxic participants in the endogenous cytokine responses (e.g. anti-TNFxcex1, anti-IL-1, anti-IFN-xcex3, or IL-1 RA); or (c) themselves inhibit or antagonize cytokine-mediated toxicity (e.g. steroids, glucocorticoids or IL-10).
The present invention is based, in part, on the surprising discoveries that, first, administration of MIF in vivo increases mortality of animals after challenge with endotoxin and, second, that inhibition of MIF activity in vivo results in enhanced or prolonged survival after either challenge with endotoxin or with TNFxcex1, which challenge would otherwise result in death due to shock. Prior to the present invention, no role for MIF in the inflammation/shock response was appreciated. Moreover, the existing evidence and observations indicated, at best, that MIF might play a beneficial role in the treatment of endotoxin-induced shock. First, MIF was shown to enhance macrophage killing of intracellular parasites and tumor cells. Second, MIF is an endotoxin-induced protein expressed by the pituitary, an organ which had previously been suggested as a source of protective rather than exacerbative factors involved in the shock syndrome. In contrast to such expectations, the Applicants have discovered that MIF activity actually exacerbates endotoxin-induced shock, and that inhibition of MIF activity can be used to successfully treat otherwise lethal effects of cytokine-mediated toxicity.
The invention is also based, in part, on the Applicants"" discovery of the role of MIF in humoral immune responses, which is demonstrated in animal models by way of a working example. In animals immunized with a test antigen in conjunction with the administration of an anti-MIF antibody, an inhibition of the development of a primary immune response to the test antigen was observed. These results indicate a means by which MIF activity modulates the primary immune response and therefore anti-MIF treatment could potentially be useful in substantially reducing an undesired immune response, such as autoimmunity and allergy. In contrast, this observation also indicates the involvement of MIF in a primary immune response. Thus, MIF may be administered as an adjuvant for an antigen during immunization of a naive individual to induce an enhanced immune response to the antigen.
The invention is illustrated by working examples which demonstrate that MIF exacerbates endotoxin-induced shock, and that anti-MIF prevents endotoxin-induced lethality in animal models. In addition, the working examples also describe the organ distribution of MIF and its receptor, the identification of a murine MIF receptor, the production of anti-MIF monoclonal antibodies, and the inhibition of immune responses by anti-MIF antibodies.